Exhaust gas emitted from an internal combustion engine, particularly a diesel engine, is a heterogeneous mixture that contains gaseous emissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”) as well as condensed phase materials (liquids and solids) that constitute particulate matter. Catalyst compositions typically disposed on catalyst supports or substrates are provided in an engine exhaust system to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components.
Sensors are provided in the engine exhaust system to measure the levels of observable conditions in the exhaust system. In particular, a soot sensor can be disposed within the engine exhaust system to measure the soot levels in the particulate filter. The internal combustion engine is controlled based on the soot sensor readings to reduce the level of soot. Thus, proper operation of the engine is based on proper operation of the soot sensor.
Accordingly, it is desirable to provide systems and methods for monitoring the functionality of the soot sensors to ensure proper operation.